Nuclear Magnetic Resonance (NMR) systems have been in use for many years and can be used to provide imaging and/or analysis of a sample being tested. For example, U.S. Pat. No. 6,160,398, U.S. Pat. No. 7,466,128, U.S. patent application Ser. No. 12/672,503, and U.S. patent application Ser. No. 12/914,138 describe a variety of NMR technologies, and are incorporated herein by reference. Various different types of NMR include medical NMR, often referred to as Magnetic Resonance Imaging (MRI), and Surface NMR (SNMR), which provides geophysical techniques for detecting subsurface liquids in the earth's crust. While there is some overlap in the technologies that may be applied in MRI and SNMR, the samples being measured and the environments in which measurements are performed are different, leading to many differences in the technologies applied.
In practice, the signals recorded by SNMR instruments can contain a combination of both “desired” and “undesired” signals. The desired signals are those particular coherent signals emitted by subsurface liquids that can be analyzed to determine the properties of the subsurface. The undesired signals are any coherent signals that complicate this analysis and may include signals from non-NMR sources as well as interfering signals from NMR sources. Existing SNMR detection techniques are generally useful for detecting desired signals in a background of white Gaussian noise. Existing SNMR detection techniques are not as useful for detecting desired NMR signals in the presence of undesired signals and other undesired interference processes.